Carbon-13 α and β hfsc are reported for a number of 2-substituted ethyl, 2-substituted 1,1-di-tert-butylethyl, and 1,1,2,2-tetrasubstituted ethyl radicals. The 13Cβ hfsc are normally in the range 11-14 G and are not much affected by polar factors, by the conformation of the 2 substituent, or by distortion of the β carbon from tetrahedral geometry. The small 13Cβ hfsc's for Me3SiCH2Ċ(CMe3)2 (9.8 G) and for n-Bu3-SiCH2Ċ(CMe3)2 (9.5 G) are attributed to distortion of the a carbon from planarity due to steric factors. The exceptionally small 13Cβ hfsc for CF3OCH2Ċ(CMe3)2 (6.1 G) is attributed to a homoconjugative interaction between the oxygen and the radical center.
The Journal of Physical Chemistry80, no. 3 (1976): 275–278.